Non-osteogenic muscle hypertrophy in children with McArdle disease

Abstract

Introduction McArdle disease is an inborn disorder of muscle glycogen metabolism that produces exercise intolerance, and has been recently associated with low values of lean mass (LM) and bone mineral content (BMC) and density (BMD) in affected adults. Here we aimed to study whether this bone health problem begins in childhood. Methods Forty children and adolescents were evaluated: 10 McArdle disease and 30 control children (mean age of both groups, 13 ± 2y). Body composition was evaluated by dual-energy X-ray absorptiometry and creatine kinase (CK) levels were determined in the patients as an estimate of muscle damage. Results Legs bone mass was significantly lower in patients than in controls (−36% for BMC and −22% for BMD). Moreover, patients had significantly higher LM values in the legs than controls, whereas no difference was found for fat mass. CK levels were positively associated with LM in McArdle patients. A correlation was found between LM and BMD variables in the control group but not in McArdle patients. Conclusion We have identified a ‘non-osteogenic muscle hypertrophy’ in children with McArdle disease. This phenomenon warrants special attention since low osteogenesis at an early age predicts a high risk for osteoporosis later in life.